REPORT OF THE CHEMST. 173 



soluble residue was left, forming the thick prairie soil of the region, 

 Tvliich has since become blackened by the decay of subsequent abun- 

 dant vegetation on it. (Iowa Geological Survey, vol. 1, 185S.) 



In the table lands of Oregon and Washington the underlying rock is 

 volcanic, and the soil arising from its disintegration is very fine in text- 

 ure, dark in color, of great fertility, and judging from the soils of simi- 

 lar origin found in the Ehine region and the Mediterranean in Europe, 

 which have supported vineyards for many years, will probably prove 

 very enduring and produce a great variety of crops. 



These two classes of soils run into each other by insensible grada- 

 tions. 



The term " prairie soils " is most indefinite as commonly used, includ- 

 ing soils of various origin. The prairie region of the West occupies a 

 vast extent of country, extending over the eastern part of Ohio, Indiana, 

 the southern portions of Michigan and Wisconsin, nearly the whole of 

 Illinois and Iowa, and the northern portion of Missouri,"* and gradually 

 passing in Kansas and Xebraska into the plains, or the arid and desert 

 region which lies at the base of the Eocky Mountains. West of the par- 

 allel of 97° and 100° the country becomes too barren to be inhabited 

 and worthless for cultivation. 



The region of the greatest cereal production of this country includes 

 the most noted of the prairie soils, and is nominally in the drift region 

 of geologists. Light clays and heavy loams are the best for wheat, 

 though very heavy clays often produce good crops, both a« to yield and 

 quality, and lighter soils may yield a good quality, but deficient in 

 quantity ; moderately stiff" soils produce generally the best crops. 



HISTORY OF THE SOELS ANALYZED BY THIS DIYISION. 



During the past year over thirty-six soils were analyzed by this divis- 

 ion. Thirty of these were analyzed completely and the results obtained 

 will be found in Table lY. The remainder were only partially analyzed, 

 and are not tabulated. 



This table is presented in the following pages, and the history of each 

 soil is appended, to be found under its respective serial number : 



